A common ingredient in permanent dyes – paraphenylenediamine (PPD) – When used as a hair color, we undergo a chemical reaction, which turns the hair dark and does not fade over time. However, this reaction can also produce protein-binding compounds in human skin, causing allergic reactions, such as eczema, facial swelling, wheezing, stomach pain, vomiting, etc. PPD can also make users sensitive to other substances, such as some chemicals in sunscreens and cosmetics. Several alternatives have been suggested, but they are generally insoluble in water and the safety of some compounds is not up to the mark. To avoid these problems, several studies have been done and a new perfect hair dye method has been proposed. The results indicated that the new hair dye had fewer allergic reactions than the traditional dye.
The team prepared seven PPD-based dyes with modifications to the aromatic amine core. Modifications have been selected to make the compounds less reactive to proteins and less likely to be absorbed into the skin. All seven compounds are permanent color models and produce a range of shades from pale pink to deep black that don’t fade, even after three weeks of daily shampooing. The team then tested the dye in a test commonly used in the cosmetic industry to
determine if the product is a skin sensitizer. Five of the denaturing dyes were “weak” sensitizers, while PPD was “moderate”. Another trial showed that the new compounds induce a reduced inflammatory response in cells compared with PPD. These results suggest that the new dye can effectively color hair and also avoid potential allergy and sensitization risks compared with other traditional dyes.
The researchers acknowledge funding from the National University of Singapore.